System and method for estimating rotor blade loads of a wind turbine

The present subject matter is directed to a method for estimating rotor blade loads, e.g. a blade root resultant moment, of a wind turbine. In one embodiment, the method includes measuring, via one or more sensors, a plurality of operating parameters of the wind turbine. Another step includes estimating out-of-plane and in-plane forces acting on the rotor blade based at least partially on the plurality of operating parameters. Further, the method includes determining an application point for the out-of-plane and in-plane forces along a span of the rotor blade. A further step includes estimating out-of-plane and in-plane moments of the rotor blade based at least partially on the out-of-plane and in-plane forces and the respective application points. Thus, the method includes calculating the load acting on the rotor blade based at least partially on the out-of-plane and in-plane moments.